Reforming of a natural cyclohexanecontaining fraction



May l0, 1966 R. M. WALDBY REFORMING OF A NATURAL CYCLOHEXANE-CONTAINING FRACTION Filed May 24, 1965 q- I` U q? U* 7l-gl HEIZINVYBHBG K dow 3G ,il BBZINVXEIHBG- ,Low

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m fl 7ll agzlNviNsdBo Nv ZO g N MOM a NII Z e IN oa 'i (D U LIJ i0/ U2 9 dow 3G N` a CC U m vo g2 s v m1 L, 9 E uw 5 l7-9I uzlzlNvxsHoslao ggg@ n Q a r| uazlNvxaHacl Z z INVENTOR o j) R. M WALDBY D m o BY M 42M Ld N LL ATTORNEYS United States Patent O 3,250,816 REFORMNG F A NATURAL CYCLOHEXANE- CQNTAINING FRACTION Roy M. Waldhy, Sweeny, Tex., vassignor to Phillips Petroleum Company, a corporation of Delaware Filed May 24, 1963, Ser. No. 282,961 Claims. (Cl. 26o-666) This invention relates to the reforming of a natural cyclohexane-containing fraction. In one aspect the invention relates to the production of additional methylcyclopentane. In one of its aspects lthe invention relates to the production `of high purity cyclohexane.

The reforming of a natural cyclohexane-containing fraction to produce methylcyclopentane is disclosed in U.S. Patent No. 3,009,002, issued to Carl M. Kron, November 14, 1961. In this patent there is disclosed a process for producing high purity cyclohexanes from naturally yoccurring cyclohexane which comprises a combination of related steps of the character such that there is produced relatively cheaply cyclohexane of a high purity (98 percent) and a benzene concentrate. The process involves -as -an essential `step the catalytic conversion of the natural cyclohexane to benzene and to methylcyclopentane` Also included in the -process is the recovery of the methylcyclopentane and benzene, and the subsequent hydrogenation of benzene to cyclohexane and isomerization of methylcyclopentane to cyclohex-ane.

Under such conditions, the natural cyclohexane is converted in a catalytic reforming zone together with and in the presence of a reformer zone feedstock, for example low end point reforming feedstock or gasoline, to produce not only more rnethylcyclopentane than can be expected from the added cyclohexane bu-t also more benzene than can tbe accounted for by the natural cyclohexane in the feed, It has been found that subjecting cyclohexane to reforming conditions results in conversion of l5 to 20 percent of the cyclohexane to methylcyclopentane with a majority of the remainder being converted to benzene. Since the ultimate desired product is generally high purity cyclohexane Which requires methylcyclopentane for its production in the isomerization zone, it would be most desirable to decrease the conversion of the cyclohexane to lbenzene and to increase Ithe conversion `of the cyclohexane to methylcyclopentane in the reforming operation.

It is an object of the invention to provide a process for the reformation of a natural cyclohexane-containing fraction.

It is Ianother object of the invention to provide a method for the production of methylcyclopent-ane.

It is yet another object of the invention to provide a process for the production of cyclohexane.

It is another object or the invention to increase the conversion of cyclohexane to methylcyclopentane in a reforming zone.

It is another object of the invention to provide a method for the decrease in the production of benzene from the catalytic reforming of cyclohexane to methylcyclopentane and benzene.

These and other objects of the invention will be readily apparent to those skilled Ain the art from the following disclosure, claims and drawing.

These objects are broadlyaccomplished in a process for reforming a natural cyclohexane-containing feed which comprises reforming said `feed in the reforming zone to produce an effluent containing ibenzene and methylcyclopentane, recovering benzene from said effluent and recycling said benzene to said reforming zone.

In another aspect of the invention, the methylcyclopentane recovered from the reforming Zone efuent, which stream contains benzene, which is detrimental when present therein above a certain minimum amount,

3,250,816 Patented May 10, 1966 ICC is introduced into a benzene hydrogenation zone and the eflluent therefrom is introduced into an isomerization zone to produce high purity cyclohexane.

The feed for the reforming zone may contain a number of hydrocarbons other than impure cyclo-hexane and usually is a mixed feed of natural C6 hydrocarbons containing isohexanes, normal hexane, benzene, methylcyclopentane, and cyclohexane as Well Aas certain heptanes, including dimethylpentanes.

In general, the feed to the reforming zone has Ibeen demethylcyclopentanized, thus obtaining a natural cyclohexane concentrate containing dimethylpentanes (which boil at approximately the same temperature as cyclohexane), with this concentrate being passed to a catalytic reforming zone. The reformer eluent is depantanized, dehexanized and the hexanes-containing stream is then subjected to solvent extraction, or the like, for the separation of benzene and methylcyclopentane fractions from the remaining reformate. The benzene-containing extract from the solvent extraction zone is then recycled to the reformer with the ratlinate being passed into a dehexanizer for the removal of normal andl isohexanes and the recovery of methylcyclopentane. The methylcyclopentane, con-taining a small percentage of benzene, is passed through a 4benzene-hydrogenation and methylcyclopentane-isomeriza-tion operation from Which the effluent is treated by conventional means to obtain a high purity cyclohexane product.

In another embodiment the natural cyclohexane-containing fraction is first dehexanized with the hexane fraction thus obtained being deisohexanized, and the deisohexanized fraction is then demethylcyclopentanized resulting in a cyclohexane and dimethylpentanes-containing fraction Which together with dehexanized-depentanized low end point gasoline heretofore described lbeing passed to the catalytic reforming zone.

Referring now to the drawing, a CG-lfeed, essentially a depentanized low end point gasoline, is passed -by conduit 2 into a dehexanizer 4. The bottoms is essentially a fraction containing the cyclohexane and dimethylpentanes with the overhead comprising norm-al hexane, benzene, and methylcyclopentane and isohexane. The overhead passes through conduit 8 into deisohexanizer 10 from which the isohexanes and lighter fraction is removed overhead through conduit 12. The bottoms pass through conduit 14 into demethylcyclopentanizer 16, the bottoms of which essentially contain cyclohexane and dimethylpentanes which are removed through conduit 18 to join the fraction in conduit 6 to pass to the reformer 46 subsequently des-cribe-d. The overhead from the demethylcyclopentanizer 16 contains essentially ,methylcyclopentane and small quantities of benzene which pass through conduit 20 to a benzene hydrogenation unit 22 Where the feed is -contacted with hydrogen (entering through conduit 24 and exiting lthrough conduit 26) under 4benzene hydrogenation condi-tions which will convert substantially all of the benzene to cyclohexane. The eluent from the benzene hydrogenation zone contains essentially cyclohexane, methylcyclopentane, and normal hexane which is passed through conduit 28 into `an isomerization zone 30. This methylcyclopentane-isomerization unit catalytically isomerizes the methylcyclopentane to cyclohexane. Any suitable catalyst system may be employed such as an aluminum halide-type catalyst. In addition, some of the n-hexane is isomerized to isohexanes. The isomerization zone eluent is passed by conduit 32 to -a demethylcyclopentanizer 34, the overhead Which contains isohexanes, normal hexane, and methylcyclopentane which is recycled to the deisohexanizer through conduit 36. The bottoms 'are passed through conduit 38 to a cyclohexane deoiler 40, the overhead 42 of which -is about 98-lpercent pure cyclo- ,D o hexane. The bottoms are essentially higher boiling materials which are removed from the process through conduit 44.

The feed to the reformer through conduit 6 is now This methylcyclopentane is ultimately isomerized to cyclohexane to form the product. The heavies, gasoline components, are removed through conduits 76 and 70.

In summary, the formation of benzene in the reformessentially a demethylcyclopentanized low end point ing step is repressed by the recycling of benzene concengasoline along with a fraction which essentially contains trate to the reforming zone so as to increase the methylcyclohexane and dimethylpentanes. The reformer concyclopentane yield, with said methylcyclopentane being ditions are such that the cyclohexane is reformed to ultimately recovered as cyclohexane. produce 'as high a percentage of methylcyclopentane as The invention is best illustrated by the following expossible. Any suitable catalyst, such as platinum-aluini- 10 ample. na, may be used. 'A pressure of 200 to 700 p.s.i.g. and a EXAMPLE temperature of 850 to 1000 F. 'is preferred. The ef- A t 1b 1 f I s 115.11 th be en re fluent from the reformer 46 is essentially methylcyclo- 1 m erlaT' lanfe a pme t1 tgh' amnz Cess pentane, benzene, isohexane,- some normal hexane, and cyhe stetig (ba e 1S omp re o e e p dimethylpentanes, which is introduced into a depentanizer W1 Wfllu e ertlzene f lyhe b 1 d t reform 50 from Which the overhead S2 contain-ing C5s and lightel?, lpra. mg W1 d e efene rfecyc o er is removed. The bottoms effluent is passed through mg W 1C 1S, m accor me? W1 ,fny mvefl lon as com' conduit 54 into a dehexanizer 56. The bottoms stream Pared to pm or art operano ,Witnout thls benzene re' from the dehexanizer 56 is essentially higher boiling gaso- Cycle 'there 1S a gross Pfot Increase of '$170000 per line materials which areremoved through conduits 57 20 day for the 697 baljfels Per day (2767 P Ounf mols Per and 70. The overhead stream from the dehexanizer is day) 0f SDZCIW Whlch are recycled t0 eXtlnClOH- There passed through conduit 58 into a zone for the recovery 1S, 0f Course, the 1055 0f bSIlZeIle 3S product but a gam Of of benzene and the separation of methylcyclopentane 777 barrels per day of cyclohexaiie product as well as a from the system. Preferably this zone is a solvent extracgain of 77 barrels per day of gasoline.

' Table 1 PROCESS WITI-I BENZENE RECYCLE FLOWS IN #-MOLS/DAY Feed Bottoms Over- Recycle Iso- Bottoms Benzene Feed to Cyclo- Gasoline, Benzene Stream component (2) (6) head (78) hexanes v (18) recycle reformer hexane 01+ (66) Isohexanes 5,780 490 5,290 650 490 Normal hexane.-. 7,580 400 l7, 180 305 424 Methyicyclopentan 3,460 110 3,350 4,262 201 66 100 Benzene 1,550 90 1,460 3 5,934 Cyclohexane 2,649 2,130 102 5,089 9,441 601 Dimethyipentan 298 315 165 7 35 410 Heptanes plus 24, 900 24, 900 24, 900

Totals 48,662 28, 937 19,725 5, 846 13, 681 137, 791 29,542 26,011

1 0.14 mols benzene recycle/mol reformer feed. 2 98.9 mol percent cyclohexane.

-Table 1I PROCESS WITHOUT BENZENE RECYCLE FLOWS IN #-MOLS/DAY Feed Bottoms Over- Recycle Iso- Bottoms Benzene Feed to Cyclo- Gasoline, Benzene Stream component (2) (6) head (78) hexanes (18) recycle reformer hexane 1+ -66) Isohexanes 5,780 490 5,290 490 Normal hexane 7,580 400 7,180 424 Mothylcyclopentanc 3, 460 110 3, 350 201 50 100 Benzene 1, 550 90 1,460 102 Cyc1ohexane 4,779 2,649 2,130 5, 089 6,931 350 Dimethy1pentanes 613 29s 315 753 35 410 Heptanes p1us 24, 900 24, 900 24, 900

Totals 48,662 28,937 19,725 31,959 17,016 25, 760

1 98,8 mol percent cyclohexane.

tion zone with benzene being recovered as the extract through conduits 64 and 66. Any means for separation of the benzene may be employed. A suitable solvent is such as triethylene glycol (Udex). A portion of the benzene is then Irecycled through conduit 68 -back into the feed to the reformer 46. The benzene recycle amount is 0.01 to 0.2 mols per mol of feed to reforming. It has been discovered that by recycling this benzene to the reformer that an increaseA in productivity of the methylcyclopentane which is isomerized lto cyclohexane product and a corresponding decrease in the production of benzene is accomplished. Since benzene, at least at present, is less valuable than cyclohexane, this is a desired advantage. The raffinate 72 from the solvent extraction zone contains essentially isohexanes, normal hexane, methylcyclopentanqand heavier boiling materials. This overhead is passed into a dehexanizer 74 from which methylcyclopentane and lighter is recycled through conduit 78 back into the feed for the deisohexanizeiA 10.

While certain examples, structures, compositions and process steps have been described for purposes of illustration, the invention is not limited to these, Variation and modification Within the scope of the disclosure and the claims can readily be effected by those skilled in the art.

I-claim:

1. A process for reforming a natural cyclohexane-containing feed which comprises reforming said feed in a -reforming zone to produce-an eiuent containing benzene and methylcyclopentane, recovering benzene from said efliuent and recycling said benzene tov said reforming zone.

2.'A process for reforming a natural cyclohexane-containing feed also containing dimethylpentanes comprising reforming said feed in a reforming zone to produce an eiuent containing benzene and methylcyclopentane, recovering benzene from said efliuent, recycling said benzene to said reforming zone, recovering a first fraction from said eiuent containing methylcyclopentane and dimethylpentanes and` recovering methylcyclopentane from said first fraction. I

3. A process for increasing the purity of methylcyclopentane produced by the reforming of a natural cyclohexane-containing feed also containing dimethylpentanes, n-hexane, benzene, and methylcyclopentane which comprises recovering from said feed a first fraction containing the cyclohexane and dimethylpentane, reforming said first fraction, recovering from the reforming zone effluent a second fraction containing benzene, yrecycling said second fraction to said reforming zone, recovering from said reforming zone effluent a lhird fraction containing methylcyclopentane, benzene, isohexanes, n-hexane, and dimethylpentanes and heavier, and recovering from said third fraction methylcyclopentane.

4. A process for rthe production of methylcyclopentane from a natural cyclohexane-containing feed also containing dimethylpentanes, n-hexane, benzene, and tmethylcyclopentane which comprises recovering from said feed a rst fraction containing n-hexane, benzene and methylcyclopentane leaving a second fraction containing the cyclohexane and dimethylpentanes, reforming said second fraction, recovering from the reforming zone an efiiuent containing methylcyclopentane, benzene, isohexanes, n-hexane, dimethylpentanes and heavier, recovering heptanes and heavier from said effluent, recovering a third fraction containing benzene from said eflluent in a solvent extraction zone, recycling said third fraction to said reforming zone, and recovering a fourth fraction from said extraction zone containing methylcyclopentane, n-hexane, dimethylpentanes and heavier, and recovering a methylcyclopentane fraction from said fourth fraction.

5. A process for the production of cyclohexane from aasdsie a natural cyclohexane-containing feed also containing dimethylpentanes, n-hexane, benzene, and methylcyclopentane which comprises recovering from said feed a first fraction containing n-hexane, benzene and methylcyclopentane leaving a second fraction containing the cyclohexane and dimethylpentane, reforming said second fraction, recovering from the reforming zone an efHuent containing methylcyclopentane, benzene, isohexanes, nhexane, dimethylpentanes and heavier, recovering heptanes and heavier from said efuent, recovering a third fraction containing benzene from said effluent in a s01- vent extraction zone, recycling said third fraction to said reforming zone, and recovering a fourth fraction from said extraction zone containing methylcyclopentane, nhexane, dimethylpentanes and heavier, recovering a methylcyclopentane fraction from said fourth fraction, subjecting said first fraction and said methylcyclopentane fraction together and in the presence of each other in a benzene-hydrogenation zone tobenzene-hydmogenation conditions, recovering a hydrogenation zone euent, then subjecting the hydrogenated eluent in an isomerization zone to methylcyclopentane-isomerization conditions, and then recovering a high-purity cyclohexane from the isomerization zone effluent.

References Cited bythe Examiner UNITED STATES PATENTS 2,766,300 10/ 1956 Weedman 260-666 2,870,083 1/1959 Elliott l 208-138 X 3,009,002 11/1961 Kron 208--79 X DELBERT E. GANTZ, Primary Examiner.

PAUL M. COUGHLAN, Examiner.

V. OKEEFE, Assistant Examiner. 

1. A PROCESS FOR REFORMING A NATURAL CYCLOHEXANE-CONTAINING FEED WHICH COMPRISES REFORMING SAID FEED IN A REFORMING ZONE TO PRODUCE AN EFFLUENT CONTAINING BENZENE AND METHYLCYCLOPENTANE, RECOVERING BENZENE FROM SAID 